Circuit Note

CN-0523

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Rev. 0 | 2 of 8

CIRCUIT DESCRIPTION

RF POWER AMPLIFIER

The CN0523 uses two HMC407 power amplifiers for its RF signal

path. The HMC407 is a gallium arsenide (GaAs), indium gallium

phosphide (InGaP), heterojunction bipolar transistor, monolithic mi-

crowave IC power amplifier operating between 5 GHz to 7 GHz for

various applications such as U-NII and HiperLAN.

Figure 2 shows the HMC407 S-Parameter performance with a typi-

cal gain of 15 dB and return losses of more than 10 dB throughout

its RF band of operation. With the two HMC407 cascaded together,

the CN0523 achieves a total system gain of 24 dB.

Figure 2. HMC407 Typical S-Parameters

The HMC407 has a 1 dB compression point (P1dB) of 25 dBm,

a third-order intercept point (OIP3) of 40 dBm, a saturated output

power of 28 dBm, and a noise figure of 5.5 dB.

Impedance Matching

The HMC407 does not require any external matching circuitry to

operate. The RFIN and RFOUT pins are single-ended with an impe-

dance of 50 Ω over the 5 GHz to 7 GHz frequency band, allowing

the CN0523 to directly interface with a 50 Ω terminated system.

Both RFIN and RFOUT have integrated DC-blocking capacitors that

allow HMC407 amplifiers to be cascaded back-to-back without the

need for external capacitors or an external matching network.

Figure 3 shows the basic configuration of HMC407 and the imple-

mentation of cascading two amplifiers.

Figure 3. Basic Connection for Cascading HMC407 Amplifiers

BAND-PASS FILTER

The first stage amplifier output is filtered by a band-pass filter,

which eliminates unwanted out-of-band amplification. The filter

used has a pass band of 5.15 GHz to 5.95 GHz, with a return

loss of 21 dB and an insertion loss of 0.7 dB at 5.8 GHz center

frequency.

RF PERFORMANCE

The resulting S-Parameters, phase noise measurements, spuri-

ous-free dynamic range (SFDR), input and output power measure-

ments, and stability measure of the CN0523 are shown in figures

below.

At the center frequency of 5.8 GHz, the CN0523 achieves a gain

of 24 dB with input and output return losses of greater than 10 dB.

Figure 4 shows the S-Parameters across the operating frequency

range.

Figure 4. CN0523 S-Parameters vs. Frequency

Figure 5 shows the corresponding noise figure of approximately 6.5

dB over the entire frequency range.