700 - 1000 MHz High Gain and Linearity Single MixerSource: Skyworks Solutions, Inc.
The SKY73032 is a high gain single mixer, optimized for base station receiver applications. The device consists of a low loss RF balun, high linearity passive mixer, and a low noise IF amplifier. An LO amplifier is also included that allow the SKY73032 to connect directly to the output of a Voltage Controlled Oscillator (VCO). This eliminates the extra gain stages needed by most discrete passive mixers. A Single Pole, Double Throw (SPDT) switch has been included to select between two different LO inputs (LO1 and LO2) for frequency hopping applications such as GSM.
RF Baluns and Passive Mixer
The RF baluns provide a single ended input, which can easily be matched to 50 Ù using a simple external matching circuit. The RF baluns offer very low loss, and excellent amplitude and phase balance. The high linearity SKY73032 is a passive, double balanced mixer that provides a very low conversion loss, and excellent 3rd Order Input Insertion Point (IIP3). Addtionally, the balanced nature of the mixer provides for high port-to-port isolation.
LO Buffers and SPDT LO Switch
The LO buffers allow the input power of the SKY73032 to be in the range of ±6 dBm. The LO section is optimized for low-side LO injection. However, each of the two LOs can be driven over a wide frequency range with only slight degradation in performance. A high isolation SPDT switch allows the SKY73032 to be used for frequency hopping applications. This switch provides greater than 40 dB of LO1 to LO2 isolation:
- LO_SEL Input LO Path Selected
- High LO1 (pin 11) enabled
- Low LO2 (pin 15) enabled
For applications that do not require frequency hopping, LO_SEL is fixed to one state and the appropriate LO input is used. An internal pull-down resistor enables the LO2 input.
The SKY73032 includes high dynamic range IF amplifiers that follow the passive mixers in the signal path. The outputs require a supply voltage connection using inductive chokes. These choke inductors should be high-Q and have the ability to handle 200 mA or greater. A simple matching network allows the output ports to be matched to a balanced 200 Ù impedance. The IF amplifiers are optimized for IF frequencies between 40 and 300 MHz. The IF amplifiers can be operated outside of this range, but with a slight degradation in performance.