UP/DOWN PHOTONIC FREQUENCY CONVERTER FOR INCOMING RADIO FREQUENCY (RF) SIGNALS BUILT INTO THE OPTOELECTRONIC OSCILLATOR (OEO)

Abstract

A compact photonic converter for radio frequency (RF) signals comprising fewer components than in the prior art. The fields of the invention are electronics, oscillating circuits, radio frequency circuits and optoelectronics. The converter comprises an optoelectronic oscillator (OEO), which is the local oscillator (LO) for the frequency conversion operation, and an RF signal injection circuit. The OEO uses a single Mach-Zehnder (MZ) electro-optic modulator and a single photodetector to enable simultaneous up/down frequency conversion of the radio frequency signal from the input of the converter. The frequency conversion is based on the intermodulation that occurs inside the MZ modulator.

Claims

1. A photonic frequency converter for values above and below an input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) comprising a photonic frequency converter (PFC) into radio frequency (RF) signals, characterized in that it is compact and comprises an optoelectronic oscillator (OEO) (1) and an injection circuit (IC) (9) of the radio frequency (RF) signal, wherein the optoelectronic oscillator (OEO) (1) being the local oscillator (LO) of the frequency conversion operation using only a single Mach-Zehnder (MZ) electro-optical modulator (3) and a single photodetector (4), which allows to perform simultaneously the frequency conversion into values above and below (down/up converter) the input radio frequency (RF) signal; and the power splitter (5) is to be connected after the single photodetector (4) and connected before a radio frequency (RF) band pass filter (6); wherein the optoelectronic oscillator (OEO) (1) comprises an optical link and a feedback loop in radio frequency (RF) domain.

2. The photonic frequency converter for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) according to claim 1, characterized in that the optical link comprises a continuous light laser source (2), the MZ electro-optical modulator (3), and the photodetector (4); and the feedback loop consists of the power splitter (5), the band-pass radio frequency (RF) filter (6), an amplifier (7) and a power combiner (8) responsible for feeding back the radio frequency (RF) input of the MZ electro-optical modulator (3).

3. The photonic frequency converter for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) according to claim 1, characterized in that the possibility of more than one signal simultaneously applied for frequency conversion, wherein each radio frequency (RF) signal source (9A) and/or (9B) will inject a signal with a certain frequency, and the outputs of these two signal sources are combined in a power combiner (10) to then be injected into the optoelectronic oscillator (OEO) through a second power combiner (8), considering, for the purpose of understanding the operation of the photonic frequency converter (PFC) proposed herein, that the optoelectronic oscillator (OEO) generates a frequency signal f.sub.0, defined by the frequency response band of the band-pass radio frequency (RF) filter (6), and the two applied signals have frequencies f.sub.1 and f.sub.2, respectively.

4. The photonic frequency converter for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) according to claim 1, characterized in that the optoelectronic oscillator (OEO) block where is generated the reference signal f.sub.0, the radio frequency (RF) signals with frequencies f.sub.1 and f.sub.2 applied from the signal source block (9A and 9B) undergoes intermodulation in the MZ electro-optical modulator (3) with the frequency signal f.sub.0 generated in the optoelectronic oscillator (OEO) (1), the intermodulation signal, with frequencies above and below the frequencies of the injected external signals (f.sub.0−f.sub.1, f.sub.0−f.sub.2, f.sub.0+f.sub.1, f.sub.1−f.sub.2, etc.) is selected by the selection filter (12A or 13A) after the power splitter (5) and amplifier (11) connected after the output of the single photodetector (4) of the optoelectronic oscillator (OEO), and after the amplifier (11) there are filters (12A) and (13A) of frequency selection above and below the f.sub.1 and f.sub.2 of the applied external signals, and the signals after the filters following the amplifier (11) represent the output signals of the photonic frequency converter (PFC) and after amplification, the signals with frequencies above and below the frequencies of the applied external signals can be used in transmission (T) and reception (R) steps.

5. The photonic frequency converter for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) according to claim 2, characterized in that the possibility of more than one signal simultaneously applied for frequency conversion, wherein each radio frequency (RF) signal source (9A) and/or (9B) will inject a signal with a certain frequency, and the outputs of these two signal sources are combined in a power combiner (10) to then be injected into the optoelectronic oscillator (OEO) through a second power combiner (8), considering, for the purpose of understanding the operation of the photonic frequency converter (PFC) proposed herein, that the optoelectronic oscillator (OEO) generates a frequency signal f.sub.0, defined by the frequency response band of the band-pass radio frequency (RF) filter (6), and the two applied signals have frequencies f.sub.1 and f.sub.2, respectively.

6. The photonic frequency converter for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) according to claim 2, characterized in that the optoelectronic oscillator (OEO) block where is generated the reference signal f.sub.0, the radio frequency (RF) signals with frequencies f.sub.1 and f.sub.2 applied from the signal source block (9A and 9B) undergoes intermodulation in the MZ electro-optical modulator (3) with the frequency signal f.sub.0 generated in the optoelectronic oscillator (OEO) (1), the intermodulation signal, with frequencies above and below the frequencies of the injected external signals (f.sub.0−f.sub.1, f.sub.0−f.sub.2, f.sub.0+f.sub.1, f.sub.1−f.sub.2, etc.) is selected by the selection filter (12A or 13A) after the power splitter (5) and amplifier (11) connected after the output of the single photodetector (4) of the optoelectronic oscillator (OEO), and after the amplifier (11) there are filters (12A) and (13A) of frequency selection above and below the f.sub.1 and f.sub.2 of the applied external signals, and the signals after the filters following the amplifier (11) represent the output signals of the photonic frequency converter (PFC) and after amplification, the signals with frequencies above and below the frequencies of the applied external signals can be used in transmission (T) and reception (R) steps.

7. The photonic frequency converter for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) according to claim 3, characterized in that the optoelectronic oscillator (OEO) block where is generated the reference signal f.sub.0, the radio frequency (RF) signals with frequencies f.sub.1 and f.sub.2 applied from the signal source block (9A and 9B) undergoes intermodulation in the MZ electro-optical modulator (3) with the frequency signal f.sub.0 generated in the optoelectronic oscillator (OEO) (1), the intermodulation signal, with frequencies above and below the frequencies of the injected external signals (f.sub.0−f.sub.1, f.sub.0−f.sub.2, f.sub.0+f.sub.1, f.sub.1−f.sub.2, etc.) is selected by the selection filter (12A or 13A) after the power splitter (5) and amplifier (11) connected after the output of the single photodetector (4) of the optoelectronic oscillator (OEO), and after the amplifier (11) there are filters (12A) and (13A) of frequency selection above and below the f.sub.1 and f.sub.2 of the applied external signals, and the signals after the filters following the amplifier (11) represent the output signals of the photonic frequency converter (PFC) and after amplification, the signals with frequencies above and below the frequencies of the applied external signals can be used in transmission (T) and reception (R) steps.

8. The photonic frequency converter for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) according to claim 5, characterized in that the optoelectronic oscillator (OEO) block where is generated the reference signal f.sub.0, the radio frequency (RF) signals with frequencies f.sub.1 and f.sub.2 applied from the signal source block (9A and 9B) undergoes intermodulation in the MZ electro-optical modulator (3) with the frequency signal f.sub.0 generated in the optoelectronic oscillator (OEO) (1), the intermodulation signal, with frequencies above and below the frequencies of the injected external signals (f.sub.0−f.sub.1, f.sub.0−f.sub.2, f.sub.0+f.sub.1, f.sub.1−f.sub.2, etc.) is selected by the selection filter (12A or 13A) after the power splitter (5) and amplifier (11) connected after the output of the single photodetector (4) of the optoelectronic oscillator (OEO), and after the amplifier (11) there are filters (12A) and (13A) of frequency selection above and below the f.sub.1 and f.sub.2 of the applied external signals, and the signals after the filters following the amplifier (11) represent the output signals of the photonic frequency converter (PFC) and after amplification, the signals with frequencies above and below the frequencies of the applied external signals can be used in transmission (T) and reception (R) steps.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The invention will be explained as an embodiment, particularly aimed at a photonic circuit in which the process of simultaneous frequency conversion of radio frequency (RF) signals into values higher and lower the frequencies of the signals applied in the converter, the solution being best illustrated in attached FIGURE, wherein is represented:

[0034] FIG. 1 is a block diagram of a simple photonic down/up converter integrated to the local oscillator (LO), based on an optoelectronic oscillator (OEO).

DETAILED DESCRIPTION OF THE INVENTION AND EXEMPLARY EMBODIMENT

[0035] The photonic frequency converter (PFC) for values above and below the input radio frequency (RF) signal integrated to the optoelectronic oscillator (OEO) and process thereof, as disclosed herein, comprises a compact photonic frequency converter (PFC) for radio frequency (RF) signals consisting of an optoelectronic oscillator (OEO) and a radio frequency (RF) signal injection circuit (IC). The optoelectronic oscillator (OEO) is the local oscillator (LO) of the frequency conversion operation and uses only a single Mach-Zehnder (MZ) electro-optical modulator 3 and a single photodetector 4, which allows for simultaneous performance of frequency conversion for values above and below (down/up converter) of the input radio frequency (RF) signal.

[0036] As shown in FIG. 1, the central dashed block 1 illustrates the optoelectronic oscillator (OEO) 1 of the frequency converter circuit. The optoelectronic oscillator (OEO) 1 is composed of a continuous light laser source 2, a MZ electro-optical modulator 3, a single photodetector 4, a power splitter 5, a band-pass radio frequency (RF) filter 6, amplifier 7 and a power combiner 8 which is responsible for feeding back the radio frequency (RF) input of the MZ electro-optical modulator 3. It is essential to note that the power splitter 5 cannot be connected to any point of the optoelectronic oscillator (OEO) 1.

[0037] The optoelectronic oscillator (OEO) 1 comprises an optical link and a feedback loop in the radio frequency (RF) domain. The optical link consists of the continuous light laser source 2, the MZ electro-optical modulator 3 and the single photodetector 4. The feedback loop in the radio frequency (RF) domain, in turn, consists of the power splitter 5, the band-pass radio frequency (RF) filter 6 with centered frequency response band on f.sub.0, the amplifier 7 and the power combiner 8. The power splitter 5 must be mandatorily connected after the single photodetector 4 and connected before the band-pass radio frequency (RF) filter 6, so that the intermodulation signal is available for its processing. This is due to the fact that only in this arrangement/configuration the band-pass radio frequency (RF) filter 6 is able to only allow the passage of signals comprised in its frequency response band, that is, it will inhibit the other various frequency components generated by intermodulation inside the MZ electro-optical modulator 3, thus preventing the operation of the optoelectronic oscillator (OEO) 1, as a local oscillator, from being disturbed.

[0038] The radio frequency (RF) signal source that will have its frequency shifted up or down is indicated by an input signal block 9, and the injection circuit (IC) 9 consists of a block representing the radio frequency (RF) signal source with frequency f.sub.1 9A and a block representing the radio frequency (RF) signal source with frequency f.sub.2 9B. Note that in the injection circuit (IC) 9 the possibility of more than one signal applied simultaneously for frequency conversion is considered. Each radio frequency (RF) signal source, 9A and 9B, will inject a signal with a certain frequency. The outputs of these two signal sources will be combined in a power combiner 10 and then injected into the optoelectronic oscillator (OEO) 1. For the purpose of understanding the operation of the photonic frequency converter (PFC) proposed herein, it should be considered that the optoelectronic oscillator (OEO) 1 generates a signal of frequency f.sub.0. The two applied radio frequency (RF) signals have frequencies f.sub.1 and f.sub.2, respectively.

[0039] In the optoelectronic oscillator (OEO) 1 block where the reference signal f.sub.0 is generated, whose value is defined by the frequency response band of the bandpass radio frequency (RF) filter 6, the applied radio frequency (RF) signals of frequencies f.sub.1 and f.sub.2 coming from the radio frequency (RF) signal blocks of frequency 9A and 9B, will undergo intermodulation with the signal of frequency f.sub.0 generated in the optoelectronic oscillator (OEO). The intermodulation signal, with frequencies above and below the frequencies of the injected external signals (f.sub.0−f.sub.1, f.sub.0−f.sub.2, f.sub.0+f.sub.1, f.sub.1−f.sub.2, etc.) is selected by filters 12A and 13A after the power splitter 5 and amplifier 11 which are connected after the single photodetector 4 of the optoelectronic oscillator (OEO). After the power splitter 5 there are filters 12A and 13A for selecting frequencies above and below the f.sub.1 and f.sub.2 frequencies of the external signals applied. The signals after the filters that follow the power splitter 5 represent the output signals of the photonic frequency converter (PFC). After amplifier 11, the signals with frequencies above and below the frequencies of the applied external signals can be used in transmission (T) 12 and reception (R) 13 steps.

[0040] To illustrate with numerical values, we consider f.sub.0=2 GHz, f.sub.1=1.3 GHz and f.sub.2=1.5 GHz. For these values as an example, we can consider the reception and transmission output spectrum with frequencies from 200 MHz (f.sub.2−f.sub.1) up to 3.5 GHz (f.sub.0+f.sub.2), with difference (f.sub.0−f.sub.1)=700 MHz and f.sub.0−f.sub.2=500 MHz; and the sum f.sub.0+f.sub.1=3.3 GHz and f.sub.0+f.sub.2=3.5 GHz. Signals with the frequency value down converted, 500 MHz (f.sub.0−f.sub.2) and/or 700 MHz (f.sub.0−f.sub.1), can be directed to signal processing steps, thus completing the reception of the signal injected into the converter. Signals with the frequency value up converted, 3.3 GHz (f.sub.0+f.sub.1) and/or 3.5 GHz (f.sub.0+f.sub.2), can be directed to signal processing steps, thus completing the transmission of the signal injected into the converter. It is worth mentioning that applying only one signal at the input of the photonic frequency converter (PFC), the power spectrum at the output, whether receiving (R) or transmitting (T), will have a smaller number of spectral components without changing its operating principle as only operations with f.sub.0 and f of the single applied signal will be counted in the definition of frequencies present at the outputs.