Nokia Mobile Phones Limited

Risto Huusko

Jouni Nyqvist

The invention relates to a frequency selective transformer circuit integrated on a multilayer printed board and operating at radio frequencies. To the input (1) of the transformer circuit there is coupled a resonant circuit realized by microstrip conductors (8, 9) operating as a two-pole filter. With the aid of the microstrip transformer according to the invention it is also possible to realize a mixer which attenuates the image frequency.

Transformer circuit having microstrips disposed on a multilayer printed

A circuit arrangement in which an RF amplifier circuit also acts as a filter for a second supply voltage which is produced from the supply voltage (V.sub.cc out) of the amplifier. The high frequency RF amplifier circuit comprises a common emitter transistor with ancillary components, and the emitter is connected through a capacitor to the ground of the circuit. From the emitter of the transistor is obtained the second supply voltage (V.sub.cc out) in which the filter circuit is said high frequency amplifier circuit wherein the transistor is used as an emitter follower. With the circuit arrangement of the invention, the separate high frequency amplifier circuit and the filtering circuit of the second supply voltage, both known of prior art, can be combined.

Circuit arrangement for connecting RF amplifier and supply voltage filter

The invention relates to a circuitry arrangement by means of which it is possible to suppress frequency components which cause spurious response in the intermediate frequency amplifier in a radio telephone receiver. The amplifier produces not only the input signal frequency but also harmonic frequencies of this frequency, in which case some harmonic frequency of the frequency component which causes spurious response is the same as the intermediate frequency. In the circuitry, between the signal path and the circuit ground, there is a circuit which is in series resonance at the frequency of the frequency component which causes spurious response, in which case a signal of this frequency is strongly attenuated, and the circuit is in parallel resonance at the intermediate frequency, in which case attenuation of a signal of this frequency is slight. It is possible to select an intermediate-frequency which is lower than the reception band multiplied by two, so that even strict requirements set on spurious response can be satisfied.

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Salo, Finland

Risto Huusko