Texas Instruments TRF1500 manual Low-BandMixer LO Input, Low-BandIF Output

Models: TRF1500

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Low-Band Mixer LO Input

SWRA004A

Low-Band Mixer LO Input

Figure 8 details the low-band mixer LO input configuration. The input power range level for the LO buffer amplifier is flexible enough (-3 dBm to -7 dBm) to drive the mixer without entering compression. The LO signal is injected through an internal LO buffer amplifier and into the mixer. A high pass shunt-L (L14) and series-C (C17) network is used for impedance matching. The inductor also shunts to ground any undesired noise that could be injected to the mixer.

Figure 8. Low-Band Mixer LO Input Configuration

Low-Band IF Output

Figure 9 details the low-band IF output configuration. The low- band mixer has a differential IF output with a 1kΩ differential output impedance. For evaluation, a 16:1 transformer balun, with a insertion loss of 1.8 dB, is used to transform the 1kΩ differential output to a single-ended output which is then matched to 50Ω. In the actual application, the IF output is usually connected to a narrow band channel select filter with a differential input and the transformer balun is not required.

The supply voltage (VCC) is applied to the IF pins with pull up inductors (L12, L13). A low-pass filter network is provided prior to the balun. The filter also acts as part of the impedance matching network. During optimization of the output matching network, it was found that mismatching the differential output, accomplished with C55, gives the best IIP3 performance with minimum effect on the gain and noise figure performance. C55 also helps to decouple the digital CMOS control line from the LO signal. The IF response is shaped by the shunt-L (L51) after the transformer balun. L51 is also used to block unwanted noise that could be reflected back to the mixer. The series capacitor (C51) near the LB_IF_OUT port is used as a dc block for evaluation purposes and does not have to be implemented in the end-users system.

TRF1500 Integrated Dual-Band RF Receiver User’s Guide

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Texas Instruments TRF1500 manual Low-BandIF Output, Low-BandMixer LO Input Configuration