## 2 Principle  
The schematic diagram of the transceiver using the proposed microwave photonic converter is shown in Figure 1. The transmitter, as well as the receiver, consists of a microwave upconverter (MUC), an electrical combiner (EC), a laser diode (LD), an MZM,an EDFA, a photodetector (PD), an electrical filter (EF), and a power amplifier (PA). The MUC upconverts the IF signal created by a digital to analog converter (DAC) to the HF signal. Next, the HF and LO signals are combined by the EC and drive the MZM to generate a modulated signal. Then, the detection of the optical signal amplified by the EDFA is implemented by the PD. Finally, the RF signal is launched by subsequent filtering and amplification. Conversely, the receiver converts the RF signal to the IF signal. The raised microwave photonic converter based on CS-DSB modulation is verified with the following steps. For upconversion, the HF (\(f_{1}\)) signal is finished by microwave upconversion of the IF (1.8 GHz) signal using a 22 GHz signal. Simultaneously, the LO (\(f_{2}\)) signal is determined by the RF signal. Thus, the transmitting RF point is generated by the beating between \(f_{1}\) and \(f_{2}\). The downconversion is accomplished through the same method. The output IF of 1.8 GHz is fixed, which is also generated by the mixing between \(f_{1}\) and \(f_{2}\). In principle, the demonstrated transceiver system presents a better ability to transmit and receive RF signals from 0.8-18 GHz in comparison with the traditional electrical transceiver system. To achieve the CS-DSB modulation, the MZM has to be biased at the minimum transmission bias (MITB) point. Taking into account the conversion condition mentioned, when we combine the HF signal and LO signal to implement the modulation of a single MZM, the optical field of the MZM can be described by  
\[E_{out}(t)=4E_{0}e^{i\frac{(\phi_{1}+\phi_{2})}{2}+i\pi+i\omega_{0}t}].[J_{0}( \beta_{LO})J_{1}(\beta_{HF})\text{cos}(\Omega_{HF}t)+J_{0}(\beta_{HF})J_{1}( \beta_{LO})\text{cos}(\Omega_{LO}t)] \tag{1}\]  
where \(E_{0}\) is the amplitude of the optical field at the MZM input, \(\omega_{0}\) is the angular frequency, \(\phi_{1}=\pi V_{\text{DC1}}/V_{\pi}\) and \(\phi_{2}=\pi V_{\text{DC2}}/V_{\pi}\) are the optical phase difference introduced by \(V_{\text{DC1}}\) and \(V_{\text{DC2}}\) which supply the bias voltages for the upper and lower arms of the MZM, \(V_{\pi}\) represents the half-wave voltage of the MZM, \(\beta_{HF}\) and \(\beta_{LO}\) represent the modulation depth of the MZM driven by HF and LO signals, respectively and, moreover, \(\Omega_{HF}\) and \(\Omega_{LO}\) are the angular frequency of HF and LO signals, respectively. Here, we ignore the higher-order sidebands (\(\geq\)2) under the small-signal modulation condition. Thus, the CS-DSB modulation of both the HF and LO signals is achieved by mathematical derivation and analyzed in Figure 2a,c. The sideband diagrams show that the optical carrier is suppressed to a low level while double sideband signals have the power of a high level. Next, the frequency conversion is realized via optical-to-electrical  
Figure 1: Schematic diagram of the transceiver using proposed microwave photonic converter (the meanings of the abbreviations in the figure are shown in Table 1). conversion and beating making use of a PD, and the photocurrent of the IF signal detected by the PD is given by  
\[i_{IF}(t)=\Re E_{out}(t)E^{*}_{out}(t)=16\Re{E_{0}}^{2}J_{0}(\beta_{LO})J_{1}(\beta _{RF})\cdot J_{0}(\beta_{RF})J_{1}(\beta_{LO})\cos[(\Omega_{RF}-\Omega_{LO})t] \tag{2}\]  
where \(\Re\) is the responsivity of the PD. Figure 2b,d prove the final conversion effect for both the upconversion and downconversion after beating.