Keywords: wcdma, cdma, rf, rfic, wireless, phone, lna, mixer, if, w-cdma, wideband cdma, sige receiver, rfics, rf ic Related Parts
APPLICATION NOTE 277
The MAX2322 Used in WCDMA Applications
Sep 01, 2000
Abstract: The MAX2322 is a high-performance SiGe receiver front-end IC optimized for PCS (1900MHz) band CDMA (code division multiple access) applications. It includes an LNA, a mixer, and a selectable frequency LO buffer. This application note presents measured performance with the MAX2322 tuned for WCDMA (wideband CDMA) applications at 2.14GHz. The intermediate frequency (IF) used in this example is 190MHz. Analysis shows the front-end gain, noise figure and third order intercept are: 18.5dB, 5.8dB and -4.1dBm respectively.
The MAX2322 is a high-performance SiGereceiver front-end IC optimized for PCS (1900MHz) band CDMA (code division multiple access) applications. It includes an LNA, a mixer, and a selectable frequency LO buffer. The LNA has three modes: high-gain high-linearity mode, high-gain low-linearity mode, and low-gain mode. These modes are controlled by LIN, GAIN, and SHDN pins. The mixer has a high IIP3 (input third-order intercept point), low noise, and a differential IF port. This application note presents measured performance with the MAX2322 tuned for WCDMA (wideband CDMA) applications at 2.14GHz. The intermediate frequency (IF) used in this example is 190MHz.
Figure 1. MAX2322 block diagram.
Application Circuit Performance
The LNA section achieves a gain of 13dB and a NF of 2dB, and the IIP3 is 8.8dBm. The input and output return losses are -11.1dB and -27.5dB, respectively. When switched into the low-gain mode, the gain decreases 10dB. Changing the bias resistor for the LNA allows the IIP3 and current consumption to be set, permitting design flexibility for your requirements.
The mixer section achieves a gain of 10.5dB and a NF of 9.3dB, and the IIP3 is 4dBm when the LO input level is -7dBm. This mixer is optimized for differential IF output, and a parallel 2kΩ resistor is needed for IF output matching. This board is tuned for 190MHz IF output and matched to 50Ωthrough a balun. On the evaluation board, a balun is used for easy interface to RF measurement equipment. The mixer also has an off-chip bias resistor. When the bias resistor is changed, IIP3 and current consumption values change.
The schematic is shown in Figure 8; the performance data
is shown in Tables 1 and 2.
Table 1. LNA Performance
(VCC = 3.0V, set high-gain and low-gain modes, BUFFEN = Low, LOX2 = Low)
