5688
The 5688 is a multi-tune high pass / low pass filter covering 130 MHz to 300 MHz. The high pass cutoff and the low pass cutoff are tuned independently, each over 32 states, so you set both edges of the passband and choose its width as well as its position. It moves to a new setting in 10 microseconds.
The filter is a surface mount part of only 0.650 x 0.375 x 0.125 inches (16.51 x 9.525 x 3.18 mm) on a 12 pad castellated footprint. It runs from a single 3.3 VDC supply drawing 3 mA and is controlled over an SPI link, with a separate select line for each section.
A fixed filter forces you to choose the passband at design time. A wideband receiver rarely wants the same slice of spectrum twice, so it ends up either letting too much through or cutting off signals it needs. Because the 5688 sets both edges under software control, one part can open wide to sweep the band and then close down around a single signal, in ten microseconds. Typical uses are tunable preselection in VHF and UHF receivers, software defined radio front ends, spectrum monitoring and signal intelligence, and co-site interference mitigation where a nearby transmitter has to be kept out of the receiver.
The centre frequency of the resulting passband is the average of the two cutoffs. The cutsheet carries a full table of the 32 x 32 combinations.
- Specifications
- Performance
- Mechanical
| Parameter | Value |
|---|---|
| Frequency range | 130 – 300 MHz |
| High pass cutoff range (f1) | 130 – 200 MHz |
| Low pass cutoff range (f2) | 210 – 300 MHz |
| Centre frequency | (f1 + f2) / 2 |
| Tuning states | 32 per section, high pass and low pass |
| Passband insertion loss, bandwidth over 50 MHz | 4.5 dB max |
| High side rejection, low pass, all states | < -30 dB |
| Low side rejection, high pass, states 0–3 | < -16 dB |
| Low side rejection, high pass, states 4–9 | < -20 dB |
| Low side rejection, high pass, states 10–15 | < -25 dB |
| Low side rejection, high pass, states 16–31 | < -30 dB |
| Impedance, input and output | 50 Ω |
| Passband VSWR | 2.5:1 |
| RF power handling, maximum | +27 dBm |
| IIP3 | +40 dBm |
| Switching speed to 90% RF power (typical) | 10 µs |
| DC voltage | 3.3 V |
| DC current | 3 mA |
| Operating temperature | -40 to +85°C |
| Control interface | SPI |
| Dimensions (L x W x H) | 0.650 x 0.375 x 0.125 in (16.51 x 9.525 x 3.18 mm) |
