A new local oscillator (LO) doubler module has been introduced that covers the 3.6 to 13.3 GHz output range in a compact 3.0" x 1.5" x 0.375" package. The doubler features internal filtering and voltage-variable output power.


The model PFDM-3R66R65-13-7R5DC-SFF takes a 3.6 to 6.65 GHz RF input signal at –3 to +3 dBm and produces a 3.6 to 13.3 GHz output signal at each of two selectable outputs with an RF output level that can be varied via a control voltage to between +13 to +20 dBm. The harmonics and sub-harmonics produced by this doubling process are filtered by the module’s internal filters to ensure that they are typically at –25 and –65 dBc, respectively.

The doubler module has dual RF outputs that are TTL switchable at a ≤20 ns rate and feature port-to-port isolation of better than 35 dB. Input and output VSWRs are typically 2.0. The module is designed to operate at +7.5 VDC with a typical operating current of 550 mA over a temperature range of –10° to +65°C.

Superior Performance in a Compact Size

The challenge of this design was to incorporate many features in a small package. Figure 1 shows the frequency doubler’s functional block diagram. There are a number of power amplification stages in order to provide +13 to +20 dBm output power for a –3 to +3 dBm input level. In addition, these stages must compensate for the filtering and component losses. The internal 7.2 to 9.8 and 9.8 to 13.3 GHz bandpass filters (BPF) utilize microstrip technology to minimize their size while maintaining high performance. The integrated filters ultimately provide better than 60 dBc spurious rejection within both doubling bands. Figure 2 shows worse-case spurious performance for both bands 1 and 2, while Figure 3 shows worse-case harmonic performance. Phase noise degradation in the doubled bands is 8 dB max. and 2 dB max. in the straight through bands when driven by a low noise LO signal.

Fig. 1 The doubler module’s functional block diagram.

Fig. 2 Worse-case spurious performance; (a) band 1 and (b) band 2.

Fig. 3 Worst-case harmonic performance.

The integrated voltage-variable attenuator offers users typically 10 dB of output level control via a single external 0 to +5 VDC control voltage. A separate input pin accepts a TTL signal to switch between the two RF outputs. The switching speed is better than 20 ns with greater than 35 dB of isolation between the two outputs. Input and output RF connectors are SMA female and are removable.

Conclusion

A compact frequency doubler module has been introduced that is designed to provide a high power LO signal covering the 3.6 to 13.3 GHz frequency range. The dual outputs are capable of being switched at a rapid rate and the output levels can be adjusted over a 10 dB range by external control voltages. The doubler module features both compact size and superior harmonic and spurious rejection. Additional information may be obtained via e-mail at sales@planarelec.com.

Planar Electronics Technology,
Frederick, MD
(301) 662-5019,
www.planarelectronicstechnology.com.