On-Wafer Measurement Setup

Fig. 4.26 shows the measurement setup where RF and LO signals are given by probes, and DC bias pads are bonding to the FR4 board through bond-wires. The PCB layout is shown in Fig. 4.27. LO signal goes through a balun to transform to differential signals. IF outputs are connected to the output buffer with a unit gain. The micrograph of the chip is shown in Fig. 4.28.

Fig. 4.27. PCB Layout.

Fig. 4.26. Measurement setup for the on wafer measurement.

4.4.2 Measurement Results

The frequencies of two RF signals and the LO signal in the measurement are 1.391 GHz, 1.392GHz, and 1.39 GHz, respectively. The power of the two RF signals is about -27dBm and the LO power is about -0.55dBm in the measurement. The circuit is still in the linear region as the RF power is -27dBm. So we can make the measurements on IIP3 accurately. The supply voltage is 1V and the standby power consumption is 0.25mW. The operation power is about 0.69mW. Fig. 4.29 shows the S11 measurement results under different LO power. As seen from the figure, the S11 is closed to simulation result. The Minimum of S11 moves to lower frequency as the LO power is increased. In our measurement that we set the LO power to -0.55dBm, nearly the same as simulation. The S11 is -18.1dB at 1.4GHz. The bandwidth is about 1GHz.

RF

LO+

LO-GND

GND

GND

GND

GND IF+

IF-

Fig. 4.28. Micrograph of the bulk-driven mixer.

0.4 0.8 1.2 1.6 2.0 2.4 2.8

0.30 0.35 0.40 0.45 0.50

-16

Voltage Conversion Gain (dB)

VGS (V) Measured SS TT

0.30 0.35 0.40 0.45 0.50

-44

0.30 0.35 0.40 0.45 0.50 -18

Fig. 4.30. The measurements of the conversion gain, the IM3 gain, and the IIP3 versus VGS. (a) voltage conversion gain. (b) the IM3 gain. (c) the IIP3.

Fig. 4.30 shows the measurement results of the voltage conversion gain, IM3 gain, and the IIP3 versus VGS. The VGS using the current mirror biasing is 0.39V. The measured data is between the SS and TT corner cases. The measured response is closed to the simulation.

Fig. 4.31 shows the gain and the IIP3 versus supply voltage VDD. In our design, the supply is set to 1V. As seen from Fig. 4.31, the bulk-driven mixer can operate at the supply voltage of 0.6V. The operation current at 0.6V is only 0.3mA corresponding to 0.18mW operation power. The voltage conversion gain is 13.2dB and the IIP3 is -2dBm.

The voltage conversion gain and the linearity versus the LO power is plotted in Fig.

4.32. Larger LO power has larger conversion gain and linearity, but the operation power is increased too. We are also interested in the LO power of -6dBm which is

0.6 0.8 1.0 1.2

12 14 16 18 20

Voltage Conversion Gain (dB)

VDD ^(V) Measured SS TT

0.6 0.8 1.0 1.2

-6 -5 -4 -3 -2 -1 0

IIP3 (dBm)

VDD (V)

Measured SS TT

(a) (b)

Fig. 4.31. The measurements of the conversion gain, and the IIP3 versus VGS. (a) voltage conversion gain. (b)IIP3.

closed to the power level in the nonlinearity calculation. With LO power of -6dBm, the voltage conversion gain and the linearity are 12dB and 0.1dBm, respectively.

Small LO power means the power consumption of the VCO can be low. So as integration of the mixer and the VCO, the whole circuit can really feature in the low power consumption.

Fig. 4.33 shows the voltage conversion gain versus the IF bandwidth. The RF

0 5 10 15 20 25 30

12 14 16 18

Voltage Conversion Gain (dB)

fIF (MHz)

Measured SS TT

Fig. 4.33. The measurements of the conversion gain versus the IF frequency.

-8 -6 -4 -2 0 2

8 10 12 14 16 18 20

Voltage Conversion Gain (dB)

PLO (dBm)

Measured SS TT

-8 -6 -4 -2 0 2

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

IIP3 (dBm)

PLO ^(dBm)

Measured SS TT

(a) (b)

Fig. 4.32. The measurements of the conversion gain, and the IIP3 versus the LO power. (a) voltage conversion gain. (b)IIP3.

frequency is fixed to 1.4GHz and the frequency of the LO signal is swept from 1.37 GHz to 1.399GHz. The measured IF bandwidth is narrower than that of the simulation.

This may come from the unknown factors in measurement setup associated with the PCB board and the external output buffer. Although the bandwidth is narrower, it still satisfies the required bandwidth of of 6 MHz in the WBAN application.

Fig. 4.34 shows the voltage conversion gain versus the RF bandwidth. The frequencies of the RF signal and LO signal change simultaneously to fix the IF frequency to 1MHz. The bandwidth is around 1.8 GHz. The voltage conversion gain is reduced as the high frequency because we have a low pass filter in the IF port.

Fig. 4.35 indicates the measurement results of the double sideband (DSB) noise figure(NF) of the bulk-driven mixer. The DSB NF is 19.65dB at the IF frequency of 10MHz. The measured DSB NF is around 3dB higher than the simulation results. This

0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 12

14 16 18 20

Voltage Conversion Gain (dB)

fRF (GHz)

Measured SS TT

Fig. 4.34. The measurements of the conversion gain versus the IF frequency.

may due to the external parasitic effects coming from the measurement setup. In the application of WBAN, the noise figure is not important because the transmission distance is usually short.

Fig. 4.36 shows the third-order intercept point. The IIP3 is around -0.5dBm using the current mirror for the bias of the circuit.

Table 4.6 summarizes the circuit performance and makes a comparison with the prior arts.

0 2 4 6 8 10

14 16 18 20 22 24 26 28 30

NF_DSB (dB)

fIF (MHz)

Measured SS TT

Fig. 4.35. The measurements of the DSB NF versus the IF frequency.

-32 -28 -24 -20 -16 -12 -8 -4 0 -90

-80 -70 -60 -50 -40 -30 -20 -10 0

Output (dBm)

PRF (dBm) IF IM3

~ -0.5dBm

Fig. 4.36. The measurements of the IF and the IM3 versus the RF power.

Table 4.6 Comparison of the proposed bulk-driven mixer with the prior arts.

RF=1.4GHz LO=

1.399GHz

[3]

Measured [3]

Measured