APPLICATION NOTE 486

MAX2388 at 190MHz IF for WCDMA


Abstract: Bench measurement data is provided for the MAX2387 WCDMA low-noise amplifier (LNA) and mixer for a 2140MHz RF and 190MHz IF. The IF output has been re-matched for 190MHz, and the new bill of materials is provided.

Additional Information

Introduction to the MAX238X

The MAX2387, MAX3288, and MAX3289 are members of a family of receive front-end devices designed for WCDMA application. They integrate a low-noise amplifier (LNA) and a high-linearity downconvert mixer in an ultra-small package. The MAX2387 and MAX2388 include a local oscillator (LO) input buffer, whereas the MAX2389 eliminates the LO buffer to provide lower current consumption.

All devices feature a high-gain and low-gain mode of operation, with a 32dB gain step for the MAX2387 and an 18dB gain step for the MAX2388/MAX2389. The ICs also include a shutdown mode for powering-down the IC.

The mixer's 3rd-order nonlinearity performance can be adjusted using an external bias resistor through the BIAS_SET pin to obtain balance between desired linearity and acceptable current consumption. For the MAX2387 and MAX2388, mixer performance is optimized for a -10dBm typical drive at the LO input buffer port. The MAX2389's mixer performance is optimized for a -4dBm typical drive at the LO input port. The LO port for all versions is configurable for either single-ended or differential operation.

Measured Performance

Most of the measurement data shown below were taken on the MAX2388 with 190MHz intermediate frequency (IF) at VCC = 2.8V. The MAX2387 and MAX2389 were verified to have similar performance.

Test Conditions:
  1. VCC = 2.8V
  2. RF input power = -30dBm
  3. RF frequency = 2140MHz; LO frequency = 2330MHz
  4. Two-tone spacing = 1MHz
  5. LO power = -10dBm (-4dBm for MAX2389)
Table 1. LNA Measurements
Parameter High Gain Low Gain Units Comments
Gain 14.6 -2.8 ( -17 MAX2387) dB LNA input loss = 0.2dB and LNA output loss = 0.2dB have been de-embedded from the measurements.
NF 1.8 7.0 dB LNA input loss = 0.2dB has been de-embedded from the measurement.
IIP3 3.5 1.0 dBm Measured with RF = -20dBm at low-gain mode
S11 -10.5 -12.9 dB 10*log10( |S11| )
S22 -13.5 -16.5 dB 10*log10( |S22| )
S12 -25.4 -12.1 dB 10*log10( |S12| )
Icc 9.9 6.8 mA  

Table 2. Mixer Measurements
Parameter High Gain Low Gain Units Comments
Gain 10.5 9.5 dB Mixer input loss = 0.2 and IF balun insertion loss = 1.0dB have been de-embedded.
NF 6.8 6.2 dB Mixer input loss = 0.2dB has been de-embedded from the measurement.
IIP3 10.0 1.8 dBm  
IIP2 17.0 16.8 dBm With single-ended LO drive
IIP2 31.2 30.5 dBm With differential LO drive
LO Leakage at IF Port -25.5 -25.5 dBm LO = -10 dBm @2330MHz MAX2387/88
LO Leakage at RF Port -45 -45 dBm LO = -10 dBm @2330MHz MAX2387/88

Table 3. S-Parameters of the LNA at High-Gain Mode
Frequency S11 S21 S12 S22
(GHz) Mag(dB) Phase(Deg) Mag(dB) Phase(Deg) Mag(dB) Phase(Deg) Mag(dB) Phase(Deg)
1.0 -2.1286 -58.278 12.847 133.75 -32.155 74.423 -0.945 -23.033
1.1 -2.3856 -62.382 12.331 131.49 -32.022 80.579 -0.964 -25.008
1.2 -2.6618 -65.862 12.154 128 -31.585 73.547 -1.089 -24.881
1.3 -2.855 69.138 11.703 126.22 -30.677 77.068 -1.285 -25.903
1.4 -3.1572 -72.628 11.296 123.77 -31.095 76.873 -1.325 -26.516
1.5 -3.4104 -75.839 11.253 120.6 -30.572 75.955 -1.467 -26.709
1.6 -3.7441 -78.872 11.206 121.03 -30.134 77.315 -1.625 -27.577
1.7 -4.1285 -82.259 10.622 117.69 -30.08 80.001 -1.798 -28.049
1.8 -4.3986 -85.465 10.986 116.13 -29.453 82.934 -1.925 -29.221
1.9 -4.7755 -89.3 10.436 115.06 -29.922 83.366 -2.098 -29.713
2.0 -5.2184 -92.921 10.444 110.19 -29.151 84.624 -2.267 -30.994
2.1 -5.6356 -96.942 10.353 108.99 -28.898 86.776 -2.345 -32.867
2.2 -6.0176 -101 10.29 105.5 -28.514 87.56 -2.451 -35.262
2.3 -6.4621 -106.27 10.58 104.32 -27.631 89.437 -2.685 -38.079
2.4 -6.9126 -111.35 9.8114 100.88 -27.764 88.93 -2.835 -42.528
2.5 -7.2807 -117.04 10.106 95.216 -27.384 88.897 -3.018 -46.811
2.6 -7.7233 -122.7 9.7148 95.186 -26.945 88.47 -3.077 -51.827
2.7 -7.9908 -130.37 9.0991 88.322 -26.888 93.211 -3.077 -57.443
2.8 -8.2315 -137.57 9.6216 84.239 -26.285 89.688 -3.257 -63.369
2.9 -8.2342 -144.27 9.0162 85.306 -26.094 95.284 -3.305 -69.697
3.0 -8.3826 -151.69 8.5833 77.645 -26.065 91.953 -3.198 -75.708

Mixer OIM3 versus RF Input Power

Test conditions are the same for the gain, IIP3, and NF measurements stated previously.

Figure 1. MAX2388 mixer IIM3 versus pin.
Figure 1. MAX2388 mixer IIM3 versus pin.

Mixer IIP3 versus VCC

The mixer features very high linearity with low current consumption. Feedback is the novel technique used to improve IIP3 with low current consumption. However, the feedback is optimized at VCC = 2.7V. If VCC deviates from 2.7V, IIP3 does not obtain the optimum value of approximately +12dBm. The following figure shows the IIP3 change versus VCC.

Figure 2. Mixer IIP3 versus VCC.
Figure 2. Mixer IIP3 versus VCC.

Test Setup

Figure 3. MAX2388 LNA IIP3 measurement.
Figure 3. MAX2388 LNA IIP3 measurement.

Figure 4. MAX2388 mixer IIP3 measurement.
Figure 4. MAX2388 mixer IIP3 measurement.

Figure 5. MAX2388 LNA NF measurement.
Figure 5. MAX2388 LNA NF measurement.

Figure 6. MAX2388 mixer NF measurement.
Figure 6. MAX2388 mixer NF measurement.

Bill of Materials for 190MHz IF Match of the Mixer (PDF, 11K)
MAX2387 Evaluation Kit (PDF, 45K)