Image-Rejected Multi-Band Frequency Down-Conversion Based on Photonic Sampling

An image-rejection multi-band frequency down-conversion scheme is proposed and demonstrated based on photonic sampling. In this scheme, two radio-frequency (RF) signal replicas with a quadrature phase difference are sampled by two ultra-short optical pulse trains in orthometric polarization via the linear electro-optic modulation in a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM). After being polarization demultiplexed, the two sampled optical pulses are separated from each other and detected by using two photodetectors (PDs), respectively. Hence, the RF signals in multiple frequency bands are simultaneously down-converted to the intermediate-frequency (IF) band. Finally, the two IF signals are combined by using an electrical 90° hybrid coupler to eliminate the image-frequency components. In the experiment, an ultra-short optical pulse train with a repetition frequency of 8 GHz is generated by employing an electrooptic modulation-based time lens with the chirp compensation, and is used to achieve photonic sampling. The experimental results indicate that image-rejection down-conversion is achieved for the input signal in the frequency range of 6 GHz to 27 GHz, where the image rejection ratio is larger than 58 dB.

We propose a photonic mixer with image rejection capability using a broadband optical source (BOS) and polarization processing. Intermediate frequency (IF) signals with image rejection are generated from the local oscillator-modulated and the time-delayed radio frequency (RF)-modulated BOS light. The RF operating frequency is flexibly tunable over a wide range by simply adjusting the time delay. In addition, the proposed system is free from dispersion-induced mixing power fading and bias drift problem. Experimental results exhibit an image rejection ratio of more than 44.6 dB for RF signals from 2 to 18 GHz, while the IF signal is fixed at 800 MHz. Image rejection mixing operation at different IF frequencies and signal power is also confirmed.

Wideband photonic microwave channelization and image-reject down-conversion

Carrier generation and IF signal up-conversion using optical injection locking and stimulated Brillouin scattering

The noise simulation circuit of noncoherent spread-spectrum system intermediate frequency (IF) signal simulator is designed based on FPGA and DSP. This circuit generates white Gaussian noise (WGN), calculates coefficients of signal-to-noise ratio (SNR) refer to the specified SNR of each channel and according to these coefficients to generate spread-spectrum IF signal for transmitting to simulate the actual receive signal of responder beacon (RSP). It has been verified that the result of test meets the requests of system.

Phase-locked loops (PLL's) may be used to implement signal combiners which coherently sum multiple signals from an array of sensors. In each combiner channel, the sensor signal is simultaneously downconverted to an intermediate frequency (IF) signal and phase-locked to an appropriately generated reference signal by a "long-loop" PLL. This loop maintains a nominal 90° phase difference between the IF signal and the reference signal irrespective of phase of the channel input (sensor output) signal. The channel IF signals are summed to generate the combiner output signal. The reference signal may be a locally generated sine wave or a delayed version of the combiner output signal. Imperfect phase control and, thus, imperfect signal combining results when noise voltages are associated with the channel signals. In this paper, a lincarized model of a PLL coherent combiner is developed. This model applies when the desired channel signals are equal amplitude and angle modulated; the channel noise voltages are equal level, Gaussian distributed, and independent; and the combiner phase errors are appropriately small. This model is then used to derive equations for the variance of differential phase errors associated with combiner operation and to show the effect of these phase errors on the average power in the combiner output signal. Relevant experimental results from a four-channel combiner are compared with the performance predicted by the linear model.

Photonic microwave harmonic down-conversion is demonstrated using an optically injected semiconductor laser operating at period-one (P1) nonlinear dynamics. In this method, the P1 oscillation is stabilized through low-frequency local oscillator signal modulation, thus generating high-order harmonics in the optical domain. Meanwhile, a radio-frequency (RF) signal is received by an intensity modulator. After the subsequent optical heterodyning, photonic microwave harmonic down-conversion can be realized. In the proof-of-concept experiment, the 4th, 6th, 9th, and 12th harmonic down-conversions are demonstrated; i.e., an RF signal with a frequency of 39GHz is down-converted to frequency-tunable intermediate frequency (IF) signals within 2GHz. The resultant IF signal mainly holds the microwave linewidth and phase noise comparable to those of the original high-frequency one.

We propose and experimentally demonstrate a photonic millimeter-wave frequency divider based on a super-harmonic injection-locked optoelectronic oscillator (OEO) and an optical frequency comb. The optical frequency comb generator is incorporated into an OEO loop to create broadband comb lines with low noise. By injecting a millimeter-wave with frequency around N times of the fundamental oscillating frequency f0 of the OEO, the injection signal can be down-converted to an intermediate frequency (IF) signal close to the oscillating frequency of the OEO. The free running OEO is synchronized with the IF signal via an injection locking mechanism. Consequently, it forms an injection-locked frequency divider as the frequency ratio between the injection signal and OEO's output signal is precisely equal to N. We carry out an experiment to divide the 45 GHz signal into 7.5 GHz and the experimental results agree well with the theoretical analysis. By changing the frequency of the injection signal, division ratio from 2 to 5 is also demonstrated on one setup. Due to the broadband spectra of the optical comb and low phase noise characteristics of the OEO, it is potential to realize very large division ratio and low phase noise for multiple input frequencies mf 0 .

In the new 4K/8K satellite broadcasting, the maximum intermediate frequency (IF) is proposed to be changed from 2071 MHz to 3224 MHz. The coaxial cable has been widely used for IF signal transmission, but the attenuation is significant with a high signal loss when a high-frequency signal is transmitted. With the increasing number of 4K/8K channels and the development of broadcasting technology, the frequency used for the IF signal will keep increasing. Therefore, the coaxial cable may not meet the future ultra-high-definition satellite broadcasting requirements anymore. Compared to the all-electrical signal transmission, the Radio-over-Fiber (RoF) system can achieve signal transmission with lower loss and reduce noise sensitivity by transmitting the signal through an optical fiber. In this work, we propose a system that uses the RoF technology to reduce the signal loss during high-frequency transmission while adopting the Power-over-Fiber (PoF) technology to generate electric power for Low-Noise Block (LNB) and RoF unit on the antenna side. A method that combines the RoF technology and PoF technology into one Double-clad Fiber is also reported. With the comparison between the signal transmitted through an RoF system and that through a coaxial cable, it can be clearly shown that the advantage of the RoF technology in the signal loss performance. The experimental results of signal transfer demonstrate that by using the RoF technology, the average amplitude of the effective signal containing TV channels increases by 8.89 dB in the range of 2224-3224 MHz, while the average amplitude increases by 5.7 dB for the effective signal in the range of 1032-2071 MHz.

This work involves in transmitting of intermediate frequency (IF) signal over fiber utilizing photonics frequency conversion, which, the main focus is the development of optical front-end receiver. The system uses photodiode and heterojunction bipolar transistor (HBT) to detect and up-convert the received IF modulated optical signal. The photodiode (PD) and HBT are very useful devices for photonics frequency conversion technique with high internal gain and frequency up conversion of optical signal. Through simulation, the optimum device parameters and characteristics were determined. The system was implemented to detect a 0.4 GHz of IF carriers signal and up-converted to 3.4 GHz of radio frequency (RF) signal. The optimum conversion gain that has been obtained from the measurement and simulation were about -11 dB and -8 dB, respectively, at V BE = 0.7 V, P LO = 4 dBm, and -25 dBm of IF optical input power. The system has been practically demonstrated and shown to agree reasonably well with both the theory and simulation. This article also refers to some recent patents on frequency conversion techniq.

Design of a low cost Schottky diode based single-balanced mixer (SBM) in full V-band with an ultra-wide intermediate frequency (IF) bandwidth is presented here. By loading multiple quarter-wavelength short-ended stubs at both radio frequency (RF) and local oscillator (LO) frequency on the multistage stepped impedance matching networks, a broadband grounding circuit is provided for IF signal and thus output power nulls are eliminated over an ultra-wide IF band. The hybrid network is constructed by a 3 dB branch coupler and a 90-degree delay line, which enables the required balanced outputs with equal amplitude and 180-degree phase difference. A prototype of the SBM is designed, fabricated and tested. Measured results demonstrate that, for RF and LO frequency over entire V-band, the mixer has a conversion loss from 6.8 to 11.4 dB with an ultra-wide IF range of 0.01–22 GHz.

We propose and experimentally demonstrate a photonic sampling-enabled multi-band microwave signals generation scheme. The intermediate-frequency input signal is up-converted to high frequency output signals in multiple frequency bands, after being optically sampled by an ultra-short optical pulse train and subsequently being detected by a photodetector (PD). The ultra-short pulse source, realized by using an electro-optic modulation-based time lens with the chirp compensation, can be flexibly adjusted to enhance the performance of multi-band frequency up-conversion. In the experiment, after optimizing the optical ultra-short pulse source with a repetition frequency of 8 GHz, ten phase-coded up-converted microwave signals with a 13-bit Barker code were successfully generated within a frequency range from 7 GHz to 41 GHz. The power fluctuation among the generated microwave signals in multi-band is measured to be 5.9 dB. The experiment results indicate that, our proposed scheme can realize the multi-band up-conversion with a high fidelity.

In this paper, the design of a continuous-time baseband sigma-delta modulator with an integrated mixer for intermediate-frequency (IF) analog-to-digital conversion is presented. This highly linear IF modulator digitizes a GSM channel at intermediate frequencies up to 50 MHz. The sampling rate is not related to the input IF and is 13.0 MHz in this design. Power consumption is 1.8 mW from a 2.5-V supply. Measured dynamic range is 82 dB, and third-order intermodulation distor- tion is 84 dB for two 6-dBV IF input tones. Two modulators in quadrature configuration provide 200-kHz GSM bandwidth. Active area of a single IF modulator is 0.2 mm in 0.35- m CMOS.

In this paper, the design of a continuous-time baseband sigma-delta (/spl Sigma//spl Delta/) modulator with an integrated mixer for intermediate-frequency (IF) analog-to-digital conversion is presented. This highly linear IF /spl Sigma//spl Delta/ modulator digitizes a GSM channel at intermediate frequencies up to 50 MHz. The sampling rate is not related to the input IF and is 13.0 MHz in this design. Power consumption is 1.8 mW from a 2.5-V supply. Measured dynamic range is 82 dB, and third-order intermodulation distortion is -84 dB for two -6-dBV IF input tones. Two modulators in quadrature configuration provide 200-kHz GSM bandwidth. Active area of a single IF /spl Sigma//spl Delta/ modulator is 0.2 mm/sup 2/ in 0.35-/spl mu/m CMOS.

For Bluetooth Low Energy (BLE) application, this paper presents the design and its measurement results of a mixed-signal phase-domain FSK demodulator in a low-IF receiver. The single-path receiver selects the intermediate frequency (IF) at a half of channel bandwidth specific for BLE frequency assignment. The proposed IF signal processing, unlike the conventional frequency discrimination, is implemented by quantizing analog signals with linear-in-phase thresholds. The mixed-signal IF processor successfully demodulates the received signals under 1-MHz data rate. It requires an SNR of 15.5 dB for a bit error rate of 0.1%. The circuits consume 1.1 mA from a single 1.8-V supply voltage with a 0.18-μm CMOS technology.