Low-Power CMOS Complex Bandpass Filter with Passband Flatness Tunability

Kim, Jung‐Ah; Lee, Yongho; Chang, Shinil; Shin, Hyunchol

doi:10.3390/electronics9030494

Cited by 8 publications

(4 citation statements)

References 15 publications

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“…The most popular approach for this is to tune the resistor-capacitor (RC) elements in a feedback path of a baseband amplifier. This is found a very popular approach in conventional RF transmitters having a narrow channel bandwidth such as, for example, a few MHz for sub-6 GHz applications [14,15] or at most a few hundred MHz for 5G applications [2]. However, since millimeter-wave RF transmitters desirably have a channel bandwidth over 1 GHz [1], the feedback-type baseband amplifier should not be appropriate because the complex switched-element feedback network induces huge parasitic elements and makes it difficult to increase the bandwidth over 1 GHz.…”

Section: Up-conversion Mixer Path and Amplitude Mismatch Calibrationmentioning

confidence: 99%

28-GHz CMOS Direct-Conversion RF Transmitter with Precise and Wide-Range Mismatch Calibration Techniques

2022

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A millimeter-wave direct-conversion radio-frequency (RF) transmitter requires precise in-/quadrature-phase (I/Q) mismatch calibration and dc offset cancellation to minimize image rejection ratio (IRR) and LO feedthrough (LOFT) for ensuring satisfactory output spectral purity. We present a 28-GHz CMOS RF transmitter with an improved calibration technique for fifth generation (5G) wireless communication applications. The RF transmitter comprises a baseband amplifier, quadrature up-conversion mixer, power amplifier driver, and quadrature LO generator. The I/Q amplitude mismatch is calibrated by tuning the gate biases of the switching stage FETs of the mixer, the I/Q phase mismatch is calibrated by tuning the varactor capacitances at the LC load of LO buffer, and the dc offset is cancelled by tuning the body voltages of the differential-pair FETs at the baseband amplifier. The proposed technique provides precise calibration accuracy by employing mV-resolution tuning voltage generation via 6-bit voltage digital-to-analog converters. It also covers wide calibration range while minimizing the impact on the circuit’s bias point and dissipated current during calibration. Implemented in a 65 nm CMOS process, the RF transmitter integrated circuit shows output-referred 1 dB compression power of +6.5 dBm, saturated output power of +12.6 dBm, and an operating band of 27.5–29.3 GHz while demonstrating satisfactory performances of −55.9 dBc of IRR and −36.8 dBc of LOFT.

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Section: Up-conversion Mixer Path and Amplitude Mismatch Calibrationmentioning

confidence: 99%

28-GHz CMOS Direct-Conversion RF Transmitter with Precise and Wide-Range Mismatch Calibration Techniques

2022

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“…Figure 4 b illustrates how the low-pass characteristics of the unit biquad are translated to the complex bandpass characteristics. The cross-interconnecting resistors R xa and R xb that are placed between the I- and Q-path biquads as shown in Figure 4 a shift the complex conjugate poles to real poles, resulting in the original low-pass filter response being shifted to the desired complex bandpass filter response, which gives the image rejection capability [ 25 ]. For optimal image rejection performance, the center frequency f o is equally set to the channel bandwidth.…”

Section: Designsmentioning

confidence: 99%

“…Then, the overall complex BPF shows a tunable gain of −22–+45 dB, tunable center frequency of 0.25–3 MHz, tunable bandwidth of 0.23–2.7 MHz, and tunable quality factor of 0.9–1.1. In addition, the passband flatness is also tunable by independently controlling the on-chip R xa and R xb in the range of 78–106 kΩ so that the band-edge gain difference is adjusted in the range of −1–+1 dB [ 25 ].…”

Section: Designsmentioning

confidence: 99%

A CMOS RF Receiver with Improved Resilience to OFDM-Induced Second-Order Intermodulation Distortion for MedRadio Biomedical Devices and Sensors

Lee

Chang

Kim

et al. 2021

Sensors

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A MedRadio RF receiver integrated circuit for implanted and wearable biomedical devices must be resilient to the out-of-band (OOB) orthogonal frequency division modulation (OFDM) blocker. As the OFDM is widely adopted for various broadcasting and communication systems in the ultra-high frequency (UHF) band, the selectivity performance of the MedRadio RF receiver can severely deteriorate by the second-order intermodulation (IM2) distortion induced by the OOB OFDM blocker. An analytical investigation shows how the OFDM-induced IM2 distortion power can be translated to an equivalent two-tone-induced IM2 distortion power. It makes the OFDM-induced IM2 analysis and characterization process for a MedRadio RF receiver much simpler and more straightforward. A MedRadio RF receiver integrated circuit with a significantly improved resilience to the OOB IM2 distortion is designed in 65 nm complementary metal-oxide-semiconductor (CMOS). The designed RF receiver is based on low-IF architecture, comprising a low-noise amplifier, single-to-differential transconductance stage, quadrature passive mixer, trans-impedance amplifier (TIA), image-rejecting complex bandpass filter, and fractional phase-locked loop synthesizer. We describe design techniques for the IM2 calibration through the gate bias tuning at the mixer, and the dc offset calibration that overcomes the conflict with the preceding IM2 calibration through the body bias tuning at the TIA. Measured results show that the OOB carrier-to-interference ratio (CIR) performance is significantly improved by 4–11 dB through the proposed IM2 calibration. The measured maximum tolerable CIR is found to be between −40.2 and −71.2 dBc for the two-tone blocker condition and between −70 and −77 dBc for the single-tone blocker condition. The analytical and experimental results of this work will be essential to improve the selectivity performance of a MedRadio RF receiver against the OOB OFDM-blocker-induced IM2 distortion and, thus, improve the robustness of the biomedical devices in harsh wireless environments in the MedRadio and UHF bands.

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“…Hence, an analog-domain calibration is needed together in order to acquire the best I/Q balance and satisfactory image rejection ratio (IRR). Moreover, the analog-domain calibration is also needed if the quadrature down-conversion scheme adopts a low IF frequency plan, because in which the image-rejection is typically done in the analog domain by using a complex bandpass filter such as [ 16 ]. In spite of the importance of the I/Q mismatch calibration issue, interestingly, we have found that it has not been often addressed in the previous millimeter-wave CMOS receiver designs for the radar applications [ 6 , 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

A 24 GHz CMOS Direct-Conversion RF Receiver with I/Q Mismatch Calibration for Radar Sensor Applications

Lee

Kim²,

Shin³

2022

Sensors

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A 24 GHz millimeter-wave direct-conversion radio-frequency (RF) receiver with wide-range and precise I/Q mismatch calibration is designed in 65 nm CMOS technology for radar sensor applications. The CMOS RF receiver is based on a quadrature direct-conversion architecture. Analytic relations are derived to clearly exhibit the individual contributions of the I/Q amplitude and phase mismatches to the image-rejection ratio (IRR) degradation, which provides a useful design guide for determining the range and resolution of the I/Q mismatch calibration circuit. The designed CMOS RF receiver comprises a low-noise amplifier, quadrature down-conversion mixer, baseband amplifier, and quadrature LO generator. Controlling the individual gate bias voltages of the switching FETs in the down-conversion mixer having a resistive load is found to induce significant changes at the amplitude and phase of the output signal. In the calibration process, the mixer gate bias tuning is first performed for the amplitude mismatch calibration, and the remaining phase mismatch is then calibrated out by the varactor capacitance tuning at the LO buffer’s LC load. Implemented in 65 nm CMOS process, the RF receiver achieves 31.5 dB power gain, −35.2 dBm input-referred 1 dB compression power, and 4.8–7.1 dB noise figure across 22.5–26.1 GHz band, while dissipating 106.2 mA from a 1.2 V supply. The effectiveness of the proposed I/Q mismatch calibration is successfully verified by observing that the amplitude and phase mismatches are improved from 1.0–1.5 dB to 0.02–0.19 dB, and from 10.8–23.8 to 1.1–3.2 degrees, respectively.

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Low-Power CMOS Complex Bandpass Filter with Passband Flatness Tunability

Cited by 8 publications

References 15 publications

28-GHz CMOS Direct-Conversion RF Transmitter with Precise and Wide-Range Mismatch Calibration Techniques

28-GHz CMOS Direct-Conversion RF Transmitter with Precise and Wide-Range Mismatch Calibration Techniques

A CMOS RF Receiver with Improved Resilience to OFDM-Induced Second-Order Intermodulation Distortion for MedRadio Biomedical Devices and Sensors

A 24 GHz CMOS Direct-Conversion RF Receiver with I/Q Mismatch Calibration for Radar Sensor Applications

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