In this paper, we present a study on a transformer-based impedance matching network. We use a simplified transformer model comprising two magnetically coupled coils, which are driven by a source and terminated by a load. The formulae of the load and the source impedance for conjugate matching of both sides of the transformer are presented, and a figure of merit is proposed for the evaluation of the power transfer efficiency of the transformer under conjugate matching conditions. Analytical expressions are provided for constructing the widely used transformer network consisting of a resistive load and a parallel tuning capacitor. To verify the proposed work, we examined various on-chip transformers implemented in 0.18 µm CMOS technology. Simulation and measurement results for a matching network synthesized using the aforementioned analytical expressions corresponded well with the result of analysis for operating frequencies up to 72% of the self-resonant frequency of the transformer. The presented results confirm that the proposed analytical formulae based on the simplified transformer model are useful for the design and optimization of transformer-based impedance matching networks in the microwave and millimeter-wave regimes.
In this paper, we present a phased-array transceiver chip operating in full X-band (8-12 GHz) in 65-nm CMOS technology. The presented transceiver for the transmit/receive module (TRM) consists of a 6-bit passive phase shifter, a 6-bit attenuator, a bi-directional gain amplifier (BDGA), and a single pole double throw (SPDT) switch connected to the internal power amplifier (PA) and the low-noise amplifier (LNA) to serve as a duplexer. A 64-bit SPI scan-chain is integrated for digital TRM control. The transmitter achieves greater than 15 dB of power gain with 11.84 dBm at the output 1-dB compression point (OP1dB). To achieve a wideband operation of the passive phase shifter, we assigned two different resonant frequencies for the phase leading and lagging networks and aligned the slopes of their phase responses to have the desired phase shifts at the center frequency. The RMS phase error is less than 5 • , and the RMS amplitude error is less than 0.45 dB for all phase and attenuation states within 8-12 GHz while dissipating 216 mW dc power from a 1 V power supply. The receiver shows greater than 15 dB of power gain and has a noise figure (NF) of less than 8.4 dB for the entire X-band. The RMS phase error and the RMS amplitude error are less than 5 • and 0.45 dB, respectively, for all control states within 8-12 GHz. The receiver consumes 110 mW with a 1 V power supply. The transceiver chip occupies an area of 4 × 1.88 mm 2 .
We report a compact single‐pull X‐band power amplifier (PA) operating at the class AB utilizing on‐chip transformers in 0.18‐μm 1P6M CMOS technology. Designed X‐band PA includes the interstage matching network and the output power combiner by utilizing on‐chip transformers to achieve small area occupation with improved power added efficiency (PAE). A series RC network is employed between gate and drain of the MOS to provide stable operation with improved bandwidth. The designed PA measures the saturated output power of 18 dBm while the achieved power gain is 19.2 dB at 8 GHz. The output 1‐dB gain compression point (OP1dB) is 14.9 dBm, and the peak PAE is measured to be 22.6% under the supply of 1.8 V. The core chip size is 0.43 mm2 excluding the pads.
We present a compact W-band power amplifier (PA) for automotive radar application in 65nm CMOS technology. The circuit adopts a pseudo-differential push-pull configuration based on transformers (TFs) which offer highly efficient and flexible matching networks with minimized area occupancy. We have set the optimal output resistance close to 50 Ω, design guidelines in sizing active devices for each stage, and the corresponding transformers were presented for optimal power efficiency based on an analysis of surrounding matching networks. Working under a supply voltage of 1.3-V, the implemented 77GHz PA achieved a 3-dB gain bandwidth of 9-GHz (72.5-81.5 GHz), a peak gain of 22.4 dB, a saturated power (Psat) of 16.4 dBm, and a peak power-added efficiency (PAE) of 20.3%. The area for the core layout is only 0.05 mm 2 , which demonstrates the highest power density among the recently reported W-band CMOS PAs.
We present a W-band 8-way wideband power amplifier (PA) for a high precision frequency modulated continuous wave (FMCW) radar in 65-nm CMOS technology. To achieve a broadband operation with an improved output power for a high range resolution and high distance coverage of FMCW radar sensors, a balanced architecture is employed with the Lange coupler which naturally combines the output powers from two 4-way push-pull PAs. By utilizing a transformer-based push-pull structure with a cross-coupled capacitive neutralization technique, the gate-drain capacitance of the 4-way PA is compensated for the stabilization with an improved power gain. Interstage matching was performed with transformers for a reduced loss from the matching network and minimal area occupation. The implemented balanced 8-way PA achieved a saturated output power (Psat) of 16.5 dBm, a 1-dB compressed output power (OP1dB) of 13.3 dBm, a power-added efficiency (PAE) of 9.9% at 90 GHz and 3-dB power bandwidth was 20.4 GHz (79.2–99.6 GHz).
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